Mechanical ASI/TC/AltimeterVSI replacement

[81X]

Kind of a strange question-  aside from a full fledged PFD such as G3x, G500, Aspens, Dynon, etc, are there options to replacing the TC/altimeter/ASI/VSI with something small like a G5?  I know I could probably  replace the TC with a digital AH but how about the ASI, altimeter, VSI?  
 

I remember seeing a photo of a Mooney panel with just two G5’s and not much of anything else (ASI, altimeter, etc., which I know is not allowed per the G5 STC, but it got me thinking.  So, I figured I’d see if anyone here knows of a path.  
 

The ironic thing is that the G5 (and probably the GI275) has the functions of all those other instruments on the G5 display. 
 

 

 

[Vance Harral]

The answer depends on the exact devices you choose.

For the G5, seems like you already answered your own question: the terms of the STC allow it to serve as a primary attitude indicator, and/or primary DG/HSI, and/or primary turn coordinator.  The terms of the STC do not allow it to serve as a primary altimeter or airspeed indicator, even though the instrument is connected to the pitot static system and can display altitude and airspeed.  If you actually saw a Mooney panel with two G5s and no ASI or altimeter, it is either illegal in terms of required instrumentation, or it has some sort of very special one-off field approval.

[carusoam]

Latest round dial replacements that have all the data possible... are GI-275s

They are a step up from the G5’s from the same company, but different division...

Often served up in pairs...

There have been a few installed around here complete with YouTube videos...

Best regards,

-a-

[201Steve]

Rob Gary in 3.....2......1.......

[Bob - S50]

Everything on the GI-275 is certified primary, but I believe you are required to install two of them if you want to remove the rest of your six pack.  The reason being that the second one which normally serves as an HSI is set up in the reversion mode so that when the AI fails (which is also displaying airspeed, altitude, VSI, heading, turn rate, and slip/skid), the HSI turns into an AI.

[81X]

8 hours ago, Bob - S50 said:

Everything on the GI-275 is certified primary, but I believe you are required to install two of them if you want to remove the rest of your six pack.  The reason being that the second one which normally serves as an HSI is set up in the reversion mode so that when the AI fails (which is also displaying airspeed, altitude, VSI, heading, turn rate, and slip/skid), the HSI turns into an AI.

Interesting, I didn’t know the 275 was STCd as primary. I wonder if that means I would need to swap out the G5’s I currently have or if I could repurpose those. 

[carusoam]

Garmin ads show multiple GI275s

Lots of data being displayed simultaneously... lots of dough for so many...

But Garmin factions make believe the G5 and the GI275 don’t exist in the same plane... so it seems...

-a-

[Ragsf15e]

The G5s don’t do much other than ADI or HSI, so maybe tough to repurpose.  Could give your copilot an adi?  
 

the 2xgi275s can replace your whole 6 pack.  Add another and it can replace primary engine instruments.  By then you might as well go with a g3x except the gi275s are really nice because they fit in the old instrument holes.

[81X]

22 hours ago, Ragsf15e said:

The G5s don’t do much other than ADI or HSI, so maybe tough to repurpose.  Could give your copilot an adi?  
 

the 2xgi275s can replace your whole 6 pack.  Add another and it can replace primary engine instruments.  By then you might as well go with a g3x except the gi275s are really nice because they fit in the old instrument holes.

After reading more, are they certified primary for the TC and VSI?  I would agree that they can replace the “T” instruments but I could t find references for the TC and ASI. 
 

That asked, after digging in more, I think your assessment is correct on the G3X where it’s about the same price and arguably nicer but requiring a new panel to be cut. 

[carusoam]

TCs aren’t making a comeback... 

They were good for making a timed turn... that was best done by holding a bank and coordination...

The bank angle is speed dependent...

 

It is so much better to use the extra hole for a second or third AI... to keep the clean side up.

The TC presentations on the modern displays are a dot here or a block there... not a whole display page of data...

As for certified... Garmin was giving the sales speech that these things are replacing the six pack... is there a way to do that and not be certified... ?

PP thoughts only, not a CFI...

Best regards,

-a-

[Vance Harral]

3 hours ago, carusoam said:

TCs aren’t making a comeback...

If you mean "traditional", standalone turn coordinators, sure.  But to be clear, IFR flight requires a rate-of-turn indicator per 91.205 (except for a few exotic corner cases with three attitude indicators, one of which works through 360 degrees of pitch and roll).  So you can't legally fly IFR unless something in your panel is certified as a primary rate-of-turn indicator.  The G5 is certified as a primary rate-of-turn indicator, I'd bet at least a dollar that the GI-275 is too.

 

4 hours ago, 81X said:

After reading more, are they certified primary for the TC and VSI?

VSI instrumentation is not required for any kind of flight, VFR or IFR.

Edited February 6, 2021 by Vance Harral

[carusoam]

Thanks Vance!

Great details you have there.

I was trying to say something similar... it just didn’t come out very well...

The individual TC instrument has been replaced by some representation on the main screens of the new glass displays...

The G5 has an obvious ball at the bottom of the screen... in some display presentation at least...

The GI275 has two bank angle targets at the top of the screen that move in relationship with speed...

So...  these instruments appear to know how to display the TC data...

Just i don’t know how to find all the details to properly answer the question...

I circled the things I believe may be the TC data and slip/skid on the GI275s...

Thanks again,

-a-

 

 

[Pasturepilot]

23 hours ago, Vance Harral said:

If you mean "traditional", standalone turn coordinators, sure.  But to be clear, IFR flight requires a rate-of-turn indicator per 91.205 (except for a few exotic corner cases with three attitude indicators, one of which works through 360 degrees of pitch and roll).  So you can't legally fly IFR unless something in your panel is certified as a primary rate-of-turn indicator.  The G5 is certified as a primary rate-of-turn indicator, I'd bet at least a dollar that the GI-275 is too.

 

VSI instrumentation is not required for any kind of flight, VFR or IFR.

https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC91-75.pdf

[Vance Harral]

16 hours ago, Pasturepilot said:

https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC91-75.pdf

I had forgotten about that AC, thanks for the reminder.

Note, however, that the absence of a TC still requires two certified attitude sources.  Not one primary AI and a Stratus, or GTX-345 with ADHARS, or Dynon pocket panel, or whatever.

[Pasturepilot]

3 hours ago, Vance Harral said:

I had forgotten about that AC, thanks for the reminder.

Note, however, that the absence of a TC still requires two certified attitude sources.  Not one primary AI and a Stratus, or GTX-345 with ADHARS, or Dynon pocket panel, or whatever.

You're welcome. It was late and I was too tired to bust out the technicalities of the AC, so I just went quick and dirty with the URL. 

[Ragsf15e]

3 hours ago, Vance Harral said:

I had forgotten about that AC, thanks for the reminder.

Note, however, that the absence of a TC still requires two certified attitude sources.  Not one primary AI and a Stratus, or GTX-345 with ADHARS, or Dynon pocket panel, or whatever.

So here’s my question about 2 gi275s replacing everything... there’s only 1 primary attitude source and the second is an hsi that can become an attitude source if the first fails but attitude isn’t continuously displayed during normal ops?  Is it just the way they wrote the stc?

 There’s only 1 continuously displayed attitude.

[Vance Harral]

1 hour ago, Ragsf15e said:

 There’s only 1 continuously displayed attitude.

Not only that, but both GI 275s are powered by the same source (the alternator), so one could argue the terms of AC 91-75 aren't met.

It's unclear to me if/how the backup batteries in these devices play into the AC.

[Bob - S50]

Just now, Vance Harral said:

Not only that, but both GI 275s are powered by the same source (the alternator), so one could argue the terms of AC 91-75 aren't met.

It's unclear to me if/how the backup batteries in these devices play into the AC.

But before you lose a GI275 you have to lose the alternator, then run the ships battery dead, then run the GI275 battery dead.  Hopefully you be on the ground by then, or at least VMC.

[Vance Harral]

29 minutes ago, Bob - S50 said:

But before you lose a GI275 you have to lose the alternator, then run the ships battery dead, then run the GI275 battery dead.  Hopefully you be on the ground by then, or at least VMC.

Sure, but we're talking about certification standards, not practical strategy.  The original conversational offshoot was about when a certified rate-of-turn indicator is legally required, and whether or not various electronic displays are certified as primary rate-of-turn indicators for this purpose.

A bit of searching around suggests to me that a pair of GI-275s are legally certified to replace the entire steam gauge 6-pack.  But I couldn't actually find the installation manual, so don't quote me on it.  Those same searches turn up posts that say actually getting rid of your steam gauge ASI, ALT, etc. may not necessarily be a good idea.  Setting aside questions of redundancy, some people feel the size of the instrument isn't kind enough to aging eyes to be a practical replacement for every individual steam gauge.  Probably not an issue if you can quickly and easily read 14pt type at 2-3 ft, but not everyone can.

[Ragsf15e]

Maybe it’s just good STC writing... if it’s approved, previous ways of doing business don't matter.